Jackman is in talks to turn up in a prominent role in the new film, which is directed by franchise stalwart Bryan Singer, according to the Hollywood Reporter. The move follows Vaughn's decision to give Jackman a cameo in First Class, which was set in the 1960s. In the Marvel comic books Wolverine is virtually ageless, allowing the character to exist in either timeline.

Quite how McKellen's Magneto and Stewart's older Professor X are to manifest in the period iteration of 20th Century Fox's long-running series is another matter: reports suggest the new film is based on the 1981 X-Men storyline, also titled Days of Future Past. It saw the present day X-Men charged with changing a key event that led to a horrifying future, in which most of them have been hunted down and killed by giant robots called Sentinels that patrol America.

Such time-bending mechanics would presumably allow both iterations of the X-Men to exist in the same movie. First Class alumni James McAvoy, Michael Fassbender, Jennifer Lawrence and Nicholas Hoult are all due to return in Days of Future Past as the younger versions of Professor X, Magneto, Mystique and Beast.

There have so far been five films in the X-Men series, with two more yet to come: as well as Days of Future Past, Jackman is currently shooting The Wolverine, which is set in the wake of the original trilogy. The films have taken more than $2bn at the global box office.